Phrase for being on an island too long

Is island fever the phrase you are looking for?

Defined as the feeling that one is stuck on an island, and doesn’t have the freedom to just go somewhere and drive for a few hours to ‘get away’. Island fever usually hits first timers that moved to the islands after six months or a year. The sudden realization that – this is all there is. Sure Hawaii is beautiful… awesome views and landmarks… but, this is it. This is home, and it’s not a big home, it’s an island.

Source: www.aimforawesome.com/hawaii/living-in-hawaii/

A more generic phrase would be "cabin fever",

an idiomatic term, first recorded in 1918, for a claustrophobic reaction that takes place when a person or group is isolated and/or shut in a small space, with nothing to do for an extended period. Cabin fever describes the extreme irritability and restlessness a person may feel in these situations.

I think it's reasonable to use that metaphorically for any claustrophobic feelings from being confined in a relatively small space, such as on an island.